Chapter 6 Underbalanced and Horizontal Drilling

Question 1

Define Underbalanced Drilling:

Answer 1

When the hydrostatic head of a drilling fluid is intentionally designed to be lower than the formation being drilled, the operation will be considered to be underbalanced drilling.

Question 2

When drilling an Underbalanced or Managed Pressure Drilling well, how many barriers to pressure should there be on the inside to the drill string

Answer 2

Two non-return valves (Float Valves)

Question 3

While drilling UBD and MPD wells, what percentage of the hole volume of kill fluid must be on location at all times and readily accessible to pump during drilling operations by opening/closing no more than two valves?

Answer 3

100%

Question 4

True or False: Underbalanced drilling utilized surface equipment to replace HP

Answer 4

True

Question 5

Why does gas migrate faster in deviated wells than in comparable vertical wells?

Answer 5

This occurs due to segregation developing in the bore hole, with the lighter fluid tending to rise on the high side of the hole whereas heavier mud moves down the low side of the hole.

Question 6

Steam chambers grow and changes over time. How do you avoid drilling into unexpected pressures when drilling in close proximity of an existing or mature SAGD operation?

Answer 6

Accurate modeling of these steam chambers must be assured prior to drilling.

Question 7

When drilling a horizontal well, what is an extra precaution that should be considered in terms of well control?

Answer 7

The MACP in multilateral wells should be calculated based on the weakest formations of all wellbores.

Question 8

The drilling and completions committee has developed a set of recommended practices, which address safety and environmental and operating guidelines for the industry. These guidelines should be used whenever UBD or MPD wells are planned and drilled.

Answer 8

IRP vol. 22- Underbalanced drilling and managed pressure drilling operations using jointed pipe.m

Question 9

Why can kick detection be difficult with MPD?

Answer 9

The closed system will want to compensate for the increased surface pressure that the influx will cause. If undetected, the choke with want to open and further reduce EBHP allowing more influx into the well.

Question 10

Prior to start-up and throughout UBD operations, the following should be conducted:

Answer 10

• A risk/failure analysis should be developed concerning the specific conditions of the well to be drilled
• Procedures should be developed for both routine and emergency kill operation.
• Frequent emergency drills should be conducted

Question 11

If the decision is made to strip out, a snubbing service maybe required:
a) During stripping operations, once the bit is directly above the blind rams.

Answer 11

• Close the blind rams
• Ensure flow is diverted to the P-tank
• Ensure pressure is bled off between the blind rams and upper pack-off prior to pulling the bit through the table.
• Change bit